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Volcanoes destroy and volcanoes create. What is a Volcano? . Opening in the Earth’s surface where magma escapes The word volcano is derived from the name of Vulcano island off Sicily, which was named after Vulcan the Roman God of Fire . What is Volcanism?.

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what is a volcano
What is a Volcano?
  • Opening in the Earth’s surface where magma escapes
  • The word volcanois derived from the name of Vulcano island off Sicily, which was named after Vulcan the Roman God of Fire
what is volcanism
What is Volcanism?

Volcanismdescribes all the processes associated with the discharge of magma, hot fluids and gases

magma or lava
Magma or Lava
  • Molten rock below the surface of the Earth that rises in volcanic vents is known as magma
  • After it erupts from a volcano it is calledlava

Commonly contains some crystals, fragments of surrounding (un-melted) rocks, and dissolved gases, but it is primarily a liquid composed principally of oxygen, silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and manganese


Red hot when it pours or blasts out of a vent but soon changes to dark red, gray, black, or some other color as it cools and solidifies.

Very hot, gas-rich lava containing abundant iron and magnesium is fluid and flows like hot tar, whereas cooler, gas-poor lava high in silicon, sodium, and potassium flows sluggishly, like thick honey in some cases or in others like pasty, blocky masses

list any contributions made by volcanoes

List any contributions made by Volcanoes

Played a key role in forming and modifying the planet

More than 80 percent of the Earth's surface--above and below sea level--is of volcanic origin

  • Gaseous emissions from volcanic vents over hundreds of millions of years formed the Earth's earliest oceans and atmosphere
  • Volcanic eruptions have produced mountains, plateaus, and plains, which subsequent erosion and weathering have sculpted into majestic landscapes and formed fertile soils
map legend

World map

  • plate boundaries (blue lines),
  • the distribution of recent earthquakes (yellow dots)
  • active volcanoes (red triangles)

Courtesy of NASA

  • Tectonic plates are composed of huge pieces of the lithosphere, (earth’s crust) that are driven by convectioncurrents in the mantle.
  • 3 types of plate boundaries; Convergent, Divergent and Transform
divergent volcanism
Divergent Volcanism
  • Occurs at mid-oceanic ridges
  • As the plates are pulled apart pillows of lava form new ocean floor
  • Non explosive with large amounts of lava
  • About 2/3 of volcanism occurs underwater @ divergent boundries
convergent volcanism
Convergent Volcanism

Oceanic-oceanic subduction zone

Produce a line of volcanoes parallel to the oceanic trench,

The chain of volcanoes is called an island arc

For Example theAleutian Island chain

convergent volcanism1
Convergent Volcanism

Oceanic-continental subduction zone

Belt of volcanoes will be generated on continental crust

The belt is then called a volcanic arc

Characterized by explosive eruptions

For Example the U.S. Pacific northwest, and the Andes of South America and the most volcanically active belt on Earth is known as the Ring of Fire

hot spots

Hot Spots

Hot spots: Regions inside a plate with active volcanism

Unlike other volcanoes, not created at plate boundaries, created within the plate interiors

For Example The Hawaiian Islands